• International Journal of Concrete Structures and Materials
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• 제5권1호
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• pp.35-42
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• 2011

In this paper, a design equation for the punching shear capacity of steel fiber reinforced concrete (SFRC) slabs is proposed based on the Japan Society of Civil Engineers (JSCE) standard specifications. Addition of steel fibers into concrete improves mechanical behavior, ductility, and fatigue strength of concrete. Previous studies have demonstrated the effectiveness of fiber reinforcement in improving the shear behavior of reinforced concrete slabs. In this study, twelve SFRC slabs using hooked-ends type steel fibers are tested with varying fiber dosage, slab thickness, steel reinforcement ratio, and compressive strength. Furthermore, test data conducted by earlier researchers are involved to verify the proposed design equation. The proposed design equation addresses the fiber pull-out strength and the critical shear perimeter changed by the fiber factor. Consequently, it is confirmed that the proposed design equation can predict the punching shear capacity of SFRC slabs with an applicable accuracy.

• Structural Engineering and Mechanics
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• 제53권1호
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• pp.41-55
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• 2015

In this paper, a model for the evaluation of shear strength of fibre reinforced polymer (FRP)-reinforced concrete beams is given. The survey of literature indicates that the FRP reinforced beams tested with shear span to depth ratio less than or equal to 1.0 is limited. In this study, eight concrete beams reinforced with GFRP rebars without stirrups are cast and tested over shear span to depth ratio of 0.5 and 1.75. The concrete compressive strength is varied from 40.6 to 65.3 MPa. The longitudinal reinforcement ratio is varied from 1.16 to 1.75. The experimental shear strength and load-deflection response of the beams are determined and reported in this paper. A model is proposed for the prediction of shear strength of beams reinforced with FRP bars. The proposed model accounts for compressive strength of concrete, modulus of FRP rebar, longitudinal reinforcement ratio, shear span to depth ratio and size effect of beams. The shear strength of FRP reinforced concrete beams predicted using the proposed model is found to be in better agreement with the corresponding test data when compared with the shear strength predicted using the eleven models published in the literature. Design example of FRP reinforced concrete beam is also given in the appendix.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.585-590
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• 2003

It analyzed the reinforcement effect according to reinforced period for FREP. It found that reinforcement effect of P-Type that was reinforced during the usage decreased compared to I-Type that was reinforced before the usage. So when reinforcing a existing structure that is being used, it should consider the stress that is produced due to the fixed load. It evaluated bending and shear of RC reinforcing beam based on the test and analytical conditions of this study. It found that stress concentration was concentrated due to rapid change of bending rigidity in reinforced cutting part as a result of excessive reinforcement thickness of FREP. It resulted in rip-off failure. It means that it should evaluate the shear when designing reinforcement.

• 콘크리트학회논문집
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• 제19권6호
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• pp.727-734
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• 2007

철근과 fiber-reinforced polymer (FRP)의 물리적, 역학적 특성의 차이 및 슬래브 상부 보강재의 기둥 인접부 집중 배근, 그리고 기둥 인접부 슬래브에 강섬유 콘크리트 (SFRC)의 타설 등에 따른 2방향 슬래브의 펀칭 전단 거동에 대한 효과를 평가하였다. 펀칭 전단강도, 강성, 연성, 변형률 분포 그리고 균열 제어 성능 등을 파악하였다. 실험 결과 기둥 인접부의 슬래브에 집중 배근을 하거나 SFRC를 타설하는 것은 glass fiber-reinforced polymer (GFRP) 바로 보강된 슬래브의 펀칭 전단 거동을 향상시켰다. 기둥 인접 구역에 집중 배근된 슬래브의 실험 결과를 다양한 설계기준과 타 연구자에 의해 제안된 예측식과 비교하였으며, 집중 배근으로 인한 이점을 예측식에 반영할 수 있도록 집중 배근된 슬래브의 철근비를 산정하는 합리적인 방법도 제안하였다.

• Steel and Composite Structures
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• 제46권1호
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• pp.115-132
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• 2023

The present study experimentally and analytically investigates the effect of tensile reinforcement ratio and arrangement on the behavior of FRP strengthened reinforced concrete (RC) beams. The experimental part of the program was comprised of 8 RC beams that were tested under four-point bending. Results have shown that by keeping the total cross-section area of tensile reinforcing bars constant, in specimens with a low reinforcement ratio, increasing the number and decreasing the diameter of bars in the section lead to 21% and 29% increase in the load-carrying capacity of specimens made with normal and high compressive strength, respectively. In specimens with high reinforcement ratio, a different behavior was observed. Furthermore, the accuracy of the existing code provisions and analytical models in predicting the load-carrying capacity of the FRP strengthened beams failed by premature debonding mode were evaluated. Herein, a model is proposed which considers the tensile reinforcement ratio (as opposed to code provisions) to achieve more accurate results for calculating the load carrying capacity of FRP strengthened RC beams.

• Computers and Concrete
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• 제4권5호
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• pp.403-424
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• 2007

The investigation of corrosion effects on the tensile behavior of reinforced concrete (RC) members is very important in region prone to high corrosion conditions. In this article, an experimental study concerning corrosion effects on tensile behavior of RC members is presented. For this purpose, a comprehensive experimental program including 58 cylindrical reinforced concrete specimens under various levels of corrosion is conducted. Some of the specimens (44) are located in large tub containing water and salt (5% salt solution); an electrical supplier has been utilized for the accelerated corrosion program. Afterwards, the tensile behavior of the specimens was studied by means of the direct tension tests. For each specimen, the tension stiffening curve is plotted, and their behavior at various load levels is investigated. Average crack spacing, loss of cross-section area due to corrosion, the concrete contribution to the tensile response for different strain levels, and maximum bond stress developed at each corrosion level are studied, and their appropriate relationships are proposed. The main parameters considered in this investigation are: degree of corrosion ($C_w$), reinforcement diameter (d), reinforcement ratio (${\rho}$), clear concrete cover (c), ratio of clear concrete cover to rebar diameter (c/d), and ratio of rebar diameter to reinforcement percentage ($d/{\rho}$).

• 한국농공학회:학술대회논문집
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• 한국농공학회 1998년도 학술발표회 발표논문집
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• pp.136-141
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• 1998

While a little research has been peformed on flexural behavior of reinforced polymer concrete (RPC)beams with the compressive strength lower than 900kg/$\textrm{cm}^2$ vary little exists in conjunction with the behavior of RPC 1,000kg/$\textrm{cm}^2$ or higher in compressive strength. In this paper the flexural performance of high strength polymer concrete beams with 1,450kg/$\textrm{cm}^2$ in compressive strength was evaluated. The unsaturated polyester resin was used to make polymer concrete as binder. The beams with stirrup singly/doubly were tested to examine the effect of tensile reinforcement ratio. As test results, reinforcement ratio increased with the increase moment strength, decreased with ultimate deflection, ductility index.

• 한국구조물진단유지관리공학회 논문집
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• 제12권5호
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• pp.81-90
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• 2008

본 연구에서는 UHPCC를 사용한 철근 콘크리트 보의 휨강도를 평가하였고, 낮은 철근비로 보강된 RC보를 포함한 휨 실험을 통해 기존의 섬유보강 콘크리트 보의 휨강도 예측식과의 일치 여부를 파악하였다. 또한 섬유보강 콘크리트에서 섬유 보강을 통한 보강철근의 대체효과를 정량적으로 평가하였다. 그 결과 ACI 544 위원회에서 제시하는 섬유보강 콘크리트를 사용한 철근보강 보의 휨강도 예측식은 압축강도 150MPa 이상의 UHPCC에 대해서는 잘 일치하지 않으며, 특히 철근비 1.5% 이하의 저보강 철근보에 대해서는 상당히 과소평가하는 것으로 나타났다. 섬유보강 콘크리트를 사용함으로써 얻을 수 있는 보의 휨내력 증가 효과는 저보강 철근보에서 상당히 큰 것으로 나타났으며, 실험결과를 바탕으로 강섬유의 특성과 철근비를 고려한 철근대체 효과 평가식을 제안하였다.

• 콘크리트학회논문집
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• 제13권3호
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• pp.195-205
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• 2001

본 연구는 화재에 노출된 철근콘크리트 부재의 휭 강도를 평가하기 위한 해석적 연구로서, 고온을 받는 단면에 대한 모멘트-곡률 관계를 구하는 것이다. 해석적 방법으로는 부재 단면에 대한 열전도 해석을 수행한 후 여러 가지 가열 조건에 대한 콘크리트와 철근의 응력-변형률 관계를 이용하여 모멘트-곡률 관계의 해석을 수행한다. 본 연구의 해석 결과는 다음과 같다. (1) 고온에 대한 철근콘크리트 부재의 잔존 휭 강도는 가열시간, 콘크리트 피복두께, 인장철근비의 영향을 받는다. (2) 고온을 받은 후의 잔존 휭 강도는 최소 철근비일 때는 상온시의 강도를 회복하지만, 최대 철근비의 50%일 때와 최대 철근비 일 때는 회복하지 않는 경향을 나타낸다. (3) 최대 철근비를 가진 철근콘크리트 부재는 가열 후 냉각상태에 대하여 철근이 항복하기 전에 콘크리트가 한계상태에 도달하는 경향을 나타낸다.

• 콘크리트학회논문집
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• 제14권6호
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• pp.830-842
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• 2002